Reaction injection moldable (RIM) thermoset polyimide elastomers

ABSTRACT

A prepolymer of the formula ##STR1## where LG is a linking group, and copolymers thereof; polymers prepared therefrom, and a reaction injection molding process employing the same.

BACKGROUND OF THE INVENTION

The present invention relates to temperature resistant thermoset plasticpolyimide elastomers and more particularly to thermally stable thermosetplastic polyimide elastomers useful in automotive power transmissionbelts which are reaction injection molded.

The temperature requirements for engine accessory drive belts haveincreased so dramatically that conventional elastomers, used tofabricate power transmission belts, are not adequate for tomorrow'sautomobiles.

The obvious solution would be to incorporate new fabricating technologyand materials into a totally new method of manufacture for powertransmission belts. This is what led us to RIM processing, short forReaction Injection Molding. This is not to be confused with theInjection Molding process which is widely used today to makethermoplastic molded parts. The Thermoplastic Injection Molding machinesimply melts the plastic and injects it into a cold mold where ithardens and assumes the desired shape of the mold. These plastics can beprocessed over and over again by remelting, and injecting them into newmolds.

The RIM machine meters two chemically reactive liquids, commonlydesignated as "A" and "B" reactants, in a precise volumetric ratio to aimpingement mixer at near sonic velocity. The reacting liquid chemicalsare then injected into a low pressure mold before they have hadsufficient time to polymerize into a solid plastic. The resultingpolymer is a fully crosslinked thermoset plastic of enormous molecularweight that can never be reprocessed again, it will thermally degradebefore remelting.

The key to the process is in the word "REACTION", i.e., (ChemicalReaction). The polymer is polymerized, created insitu, in the mold bythe spontaneous chemical reaction of two liquid oligomer systems witheach other. I use the term oligomer system because neither the A or Bside is a completely finished polymer. The A and B components areblended chemical intermediates which are liquid and have no chemicalreactive to themselves at the processing temperature. The two oligomerintermediates do, however, react very with each other upon mixing.Typical reaction times of 0.2 to 1 second are not uncommon. Finished,completely cured parts are commonly molded in 1 to 2 minutes.

Polymer technology has not kept pace with RIM technology. There a numberof RIM polyurea and polyurethane materials which satisfy the basicphysical characteristics required in these applications, namely, tensilestrength, flexural modulus, hardness, and elongation. In addition, theyhave superior dynamic properties over conventional millable gumelastomers such as Neoprene, Hycar. and Hypalon. They do not, however,have the temperature resistance necessary for automotive powertransmission belts.

Thermal degradation studies conducted on these elastomers clearly showthe thermally weak part to be the urethane or urea linkage. The polymerbackbone structures are capable of withstanding much highertemperatures. The polythioether backbones are stable to about 600° F.,aliphatic polyethers are stable to about 670° F., and aromaticpolyethers are stable at temperatures in excess of 700° F. Oligomericdiamines used to formulate polyureas would satisfy all the requirementsfor power transmission belts if a more heat resistant chemical linkagecould be found. It would also satisfy all of the manufacturingrequirements if the new chemical linkage would form insitu by RIMprocessing. In accordance with the present invention, these oligomericprepolymers are terminated by a maleimide, itaconimide, citraconimide,triazolinedione, or vinylketone and the conventional linkages of thepolyurethane or polyurea have been replaced by a much more stablelinkage formed by Michael Addition or Diels Alder reaction with thesemoieties.

Polymers formed by Michael (nucleophilic) Addition of a bismaleimide oritaconimide are known in the art. White, J.E. et al., "Reactions ofDiaminoalkanes with Bismaleimides: Synthesis of Some Unusualpolyimides," J. Appl. Poly Sci., 29, 891-99 (1984) discloses thatpolyimide elastomers can be obtained by reacting diaminoalkanes havingflexible backbones with aliphatic and aromatic bismaleimides. Examplesof the diaminoalkanes are 1,8-diaminoctane,N,N-dimethyl-1,6-hexanediamine.

I have discovered that these also hold true with the bisitaconimides. Infact I have found that the bisitaconimides behave and performidentically to the bismaleimides, and the resulting 3-methylsuccinimidelinkage is much more stable than the succinimide linkage formed by thebismaleimides. ##STR2##

This is due to the location of the double bismaleimide, the bond islocated in the ring, and the linkage resulting from the Michael Additionto a primary amine leaves a tertiary hydrogen attached to thesuccinimide ring. The itaconimide on the other hand has its unsaturatedbond between a pendant methyl group and the succinimide ring. Onreacting with a primary amine the amine is directed to attach directlyto the succinimide ring leaving a pendant methyl group rather than atertiary hydrogen. The pendant methyl group is far more thermally stablethan a tertiary hydrogen and it adds flexibility and resilience to thepolymer.

U.S. Pat. No. 3,741,942 to Crivello (1973) teaches a polyimide obtainedby reaction of a bismaleimide and a dithiol, however, these polyimides,while temperature resistant, do not have the other physical propertiesrequired for use in automotive power transmission belts and there is nodisclosure of RIM processing of the polyimides.

Bismaleimides have also been used to crosslink unsaturated rubbers asdescribed in U.S. Pat. No. 2,989,504 to Little (1961), and they havebeen reacted with diamines by Michael Addition in making fibers andmolded articles as described in U.S. Pat. No. 2,818,405 to Kovacic(1957), U.S. Pat. No. 3,658,764 to Lyon (1972). U.S. Pat. No. 3,767,626to Bron (1973), and U.S. Pat. No. 3,878,172 to Bargain et al. (1975),and RE 29,316 to Bargain et al. (1976).

U.S. Pat. No. 3,738,967 to Crivello (1973) teaches that polyimides canalso be prepared by a nucleophilic addition reaction of a bismaleimideand hydrogen sulfide. These polyimides are disclosed as being useful inmolding, insulation, and coating. Another class of polyimide is obtainedby reacting a bismaleimide with a diamine and then a sulfide or dithiolaccording to U.S. Pat. No. 3,766,138 to Crivello (1973).

SUMMARY OF THE INVENTION

A principal object of the present invention is to provide a thermallystable elastomer having the requisite performance characteristics foruse in power transmission belts.

Another subject of the present invention is to provide a thermallystable elastomer which can be prepared and molded by reaction injectionmolding.

A further object of the present invention is to provide liquid oligomerswith bismaleimide, bisitaconimide, biscitraconimide, bistriazolinedione,or bisvinylketone terminations which are useful in reaction injectionmolding to provide thermally stable elastomeric articles.

A still further object of the present invention is to provide thermallystable power transmission belts which are prepared using the elastomersdescribed herein.

Another object of the present invention is to provide a reactioninjection moldable bismaleimide, bisitaconimide, biscitraconimide,bistriazolinedione, or bisvinylketone oligomeric prepolymer.

Another object of the present invention is to provide a process forreaction injection molding wherein the bismaleimide, biscitraconimide,bisitaconimide, bistriazolinedione, or bisvinylketone terminatedprepolymers described herein are reacted with a dinucleophile to preparearticles of the temperature resistant elastomers described herein.

These and other objects are achieved in the present invention whichprovides:

A polyimide having one of the following repeating units in the formula.##STR3## where

W is a member having in its backbone a chain selected from the groupconsisting of a polyether, polythioether, polyetherthioether,polycarbonyl, or a copolymer thereof; and more particularly ##STR4##

x is a carbon or nitrogen atom and when x is a carbon atom, one carbonatom may be substituted by a methyl group;

m is 1 to 13 and preferably 4 to 13;

n is 1 to 5;

Where LG is a linking group and preferably a group of the formula:##STR5##

Where L represents a flexible linking group and more particularly agroup having one of the following structures: ##STR6##

Where u is 1 to 7 and preferably 1,3, or 7; t is 1 to 5 and preferably 1or 3.; m is 1 to 13 preferable 4 to 13;

L may also represent an alkylene bridge of 1 to 5 carbon atoms such asmethylene, ethylene, etc.; or L may be represented by the followingformulas: ##STR7## where E is --O--, ##STR8##

m is defined as above, p is 3 or 5; and Ar represents an aryleneincluding alkarylene such as phenylene and bis isopropylenephenylene.

The linking group LG and L are usually divalent, however, trivalent andtetravalent linking groups such as ##STR9##

N,N,N',N', -tetrakis(3-etherpropyl)ethylenedamine are also possible.When the linking group is trivalent or tetravalent, the A component maycontain 3 or 4 bismaleimide, bisitaconimide or like groups. It isdoubtful that the latter linking groups would be used since it would bemore expedient to introduce crosslinking into the polymer by using apolyvalent dinucleophile.

W represents a oligomer of between 500 and 6,000 in molecular weight. Itcan be an aliphatic polyether, polythioether, polyetherthioether, or apoly-metaphenylether. W may also represent a co-polymer of two or moreof these moieties. When W is a branched chain moiety, there may be 2 to4 reactive terminal groups.

A bismaleimide, bisitaconimide, biscitraconimide, bistriazolinedione,and bisvinylketone terminated oligomeric prepolymer with one of thefollowing formula. ##STR10##

A temperature resistant elastomer prepared by reacting a bismaleimide,bisitaconimide, biscitraconimide, bistriazolinedione, or bisvinylketoneterminated prepolymer of the formulas (X)-(XIV) with a dinucleophile ina Michael Addition or a Diels Alder Addition polymerization.

DETAILED DESCRIPTION OF THE INVENTION

Temperature resistant elastomeric polyimides in accordance with thepresent invention are prepared by reacting any of the prepolymers offormulas (X), (XII), (XII-A), (XIII) or (XIV) above with a dinucleophilein a Michael Addition or Diels Alder reaction.

A particular advantage of the present invention is that the prepolymersof the formulas (X), (XII), (XII-A), (XIII) or (XIV) are useful inreaction injection molding. Hereinafter, the prepolymers of the formulas(X), (XII), (XII-A), (XIII) or (XIV) will be referred to as the "Acomponent" and the dinucleophile will be referred to as the "Bcomponent".

In (RIM), it is essential that both the A and B components be a lowviscosity liquid at the process temperature, preferable no greater than10,000 centipoise at 110° C. There stoichiometric ratios must bereasonably close, no greater than 3 to 1, preferable 1.5 to 1. The A andB components must be low enough in molecular weight, preferable between600 and 5,000, to impart sufficient molecular mobility to permitcomplete polymerization in 60 seconds, preferably in 10 to 20 seconds.

All of these factors are important. If one or more of these parametersare out of range the following may result:

1. Too slow on reaction time, premature reaction shutdown, or stickyproduct, most likely the molecular weights of both the A and Bcomponents are too great.

2. Sticky, gelatinous soup, is generally the result of improperstoichiometric rations.

3. Fully cured parts with veins of sticky material mixed throughout orhard and soft areas in the same part, is most like caused by poormixing. This can occur when the stoichiometric ratios are too far apartof if there is a great difference between the viscosities of the A and Bcomponents.

In accordance with the present invention, two approaches have beenadopted with respect to the design of component A. Formula (X)represents bismaleimides, XII-A represents bisitaconimides, XIIIrepresents biscitraconimides and XIV represents bistriazolinedioneswhich are liquid under the RIM reaction conditions. Due to the symmetryof these compounds, there is a tendency for the compounds to becrystalline solids. In accordance with the present invention, however,the compounds are designed with a flexible linking group L between themaleimide moieties which places a sufficient internuclear distancebetween the rings and provides sufficient flexibility to the moleculethat the compounds are liquid under the RIM reaction conditions.

In order to provide sufficient flexibility and internuclear distance inprepolymers of the formula (V), L is preferably an aromatic ether group,an aliphatic ether group or aromatic ether groups alternating with shortaliphatic chains. The aliphatic chains between ether linkages preferablyhaving 4 to 13 carbon atoms. The aromatic ether preferably includes ameta substituted phenylene as opposed to a para or ortho substitutedphenylene because meta substitution provides substantially lower meltingpoints in the A component and much greater flexibility to the linkinggroup.

PROCEDURE: A solution containing 1.0 mole equivalent of an aromaticprimary diamine terminated aliphatic ether oligomer, in dry acetone wasadded drop wise to a mechanically stirred solution of dry acetone and2.0 moles of itaconic anhydride at 12° C. After the addition step hasbeen completed, the solution is allowed to warm to 27° C. and iscontinuously stirred for an additional 4 hours. A cream off-whiteprecipitate will form and the reactor solution will become very thick.

To the reactor is added 0.2 moles of sodium acetate and 4 moles ofacetic anhydride. The reactor solution will turn bright yellow almostimmediately and most of the diamic acid precipitate will be dissolved in4 hours. The reactor is allowed to stir overnight or 12 hours.

The sodium acetate is then filtered out and the filtrate is added slowlyto a rapidly stirred solution of 4 moles of sodium carbonate in icewater. The product is then redissolved in acetone and the wash cycle isrepeated. The wash cycle is repeated until all of the acetic acid hasbeen removed. The product is then transferred to a wiped column highvacuum still to remove all traces of water.

Selection of the dinucleophile or B component will depend to a largedegree on the nature of the A component. Where the A component is arelatively low molecular weight compound of the formula (V), highermolecular weight B component may be used in the RIM process. On theother hand, where the A reactant is a higher molecular weight prepolymerof the formula (X) or (XIV), a lower molecular weight dinucleophile willbe selected.

Dinucleophiles useful in providing thermoset elastomers by RIMprocessing can be more particularly represented by formulas: ##STR11##

Where R is a hydrogen atom or a lower alkyl group (e.g., an alkyl groupcontaining 1 to 4 carbon atoms), and W' is a polyether, aromatic oraliphatic, aliphatic polythioether, aliphatic polyetherthioether or aco-polymer of aromatic and aliphatic polyethers or polythioethers whichpreferably do not substantially degrade upon heating to temperatures ofat least 350° F. and more preferably at least 400° F. More particularlyW' can be represented by the formulas (XVII)-(XIX).

    --R.sup.1 --(--O--R.sup.2 --S--R.sup.3 --).sub.x --        (XVII)

    --(--R.sup.1 --O--R.sup.2 --).sub.x --                     (XVIII)

    --(--R.sup.1 --S--R.sup.2 --).sub.x --                     (XIX)

Here R¹, R², and R³ represent straight or branched chain alkylene orarylene groups 2 to 13 carbon atoms, x is a function of the totalmolecular weight divided by the molecular weight of the repeating units.The total molecular weight is most generally between 500 and 6,000 and xis typically between 2 and 70. As a general rule, the dinucleophilesvary in reactivity as follows: aromatic primary amines greater thanaliphatic primary amines, primary amines greater than secondary amines.Mercaptans are very slow to react. Consequently, when they are used inthe RIM process, a tertiary amine such as quinuclidine ortriethyldiamine is added to the A component as a catalyst. Triethylaminemay also be used as a catalyst but it tends to be too volatile. All ofthe following dinucleophiles have been used for W'.

Representative examples of dinucleophiles are provided in the followingtable.

                                      TABLE                                       __________________________________________________________________________     1.                                                                              ##STR12##                                                                    Where n = 1 to 9                                                             2.                                                                              ##STR13##                                                                   3.                                                                              ##STR14##                                                                   4.                                                                              ##STR15##                                                                     ##STR16##                                                                   5.                  JEFFAMINE T-5000 (Texaco Corp.)                             ##STR17##         [C.A.S. Registry No. 64852-22-8] Were x + y + z =                             27                                                        6.                  JEFFAMINE D-Series (Texaco Corp.)                           ##STR18##                                                                                        ##STR19##                                                7.                                                                             JEFFAMINE ED-Series (Texaco Corp.)                                             ##STR20##                                                                     ##STR21##                                                                   8.                                                                             UNILINK 4200 (U. O. P. Corp.)                                                  ##STR22##                                                                   9.                                                                             UNILINK 4100 (U. O. P. Corp.)                                                  ##STR23##                                                                  10.                                                                             UNILINK XPA SERIES (U. O. P. Corp.)                                            ##STR24##                                                                  MATERIAL CODE        R.sub.1                                                                             R.sub.2                                            XPA-23               C'.sub.8                                                                            C'.sub.8                                           XPA-24               C.sub.8                                                                             C.sub.8                                            XPA-28               C.sub.6                                                                             C.sub.6                                            WHERE:                                                                                              ##STR25##                                                                     ##STR26##                                                                     ##STR27##                                                 BIS-ANILINE M (Mitsui Petrochemicals)                                          ##STR28##                                                                    4,4'-bisaminocumyl m-benzene                                                  DYTEK ™ A (Du Pont)                                                         ##STR29##                                                                    2-methylpentamethylenediamine                                                 BHMT (Du Pont)                                                                H.sub.2 NCH.sub.2 (CH.sub.2).sub.4 CH.sub.2 NHCH.sub.2 (CH.sub.2).sub.4       CH.sub.2 NH.sub.2                                                             bis-hexamethylenetriamine (BHMT)                                              C.sub.12 DIAMINE (Du Pont)                                                    H.sub.2 NCH.sub.2 (CH.sub.2).sub.18 CH.sub.2 NH.sub.2                         1,12-dodecanediamine                                                          DPTA (Du Pont)                                                                NH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 NHCH.sub.2 CH.sub.2 CH.sub.2              NH.sub.2                                                                      dipropylenetriamine (DPTA)                                                    TAPA (Du Pont)                                                                 ##STR30##                                                                    tris(3-aminopropyl)amine (TAPA)                                               TAPED (Du Pont)                                                                ##STR31##                                                                    N,N,N',N'-tetrakis(3-aminopropyl)ethylenediamine (TAPED)                      Aldrich Chemical Company                                                      H.sub.2 N(CH.sub.2).sub.13NH.sub.2                                            1,13-Tridecanediamine                                                         Aldrich Chemical Company                                                      H.sub.2 N(CH.sub.2).sub.9NH.sub.2                                             1,9-Nonanediamine                                                           __________________________________________________________________________

W can also be formed from any of the polythioethers described in U.S.Pat. No. 4,366,307 to Singh et al. which is incorporated herein byreference.

These prepolymers react with dinucleophiles by a Michael Addition orDiels Alder addition to afford the elastomers, for use in RIM processes,the prepolymer must be a free flowing liquid below 250° F. Preferably,this reaction proceeds under conditions compatible with the RIM process.

Typical RIM processing conditions vary because of the differences inproperties of the reactants and of the chemistry of the reactions, eachmaterial requires different processing conditions. Typical prepolymertemperatures ranged from 160° to 265° F. The higher temperatures, inexcess of 230° F., were avoided whenever possible for two reasons. Firstof all bismaleimides, bisitaconimides, biscitraconimides,bistriazolinediones, and bisvinylketones have a tendency to react withthemselves. The higher the temperature the more rapid the reaction,hence, shorter pot life. This is further aggravated by the high pumpingpressure of the RIM injectors. The second reason involves the seals onthe RIM machine, above 265° F. these seals begin to fail rapidly.Leaking material reduces injection pressure and upsets thestoichiometric ratio between the two components.

Mixing ratio control is important. Because the RIM process depends on achemical reaction to achieve its finished properties, the stoichiometricratio of the A component to the B component is important to insure thatall of the reactive sites have indeed reacted and that you have achievedthe maximum possible polymer networking and molecular weight. This ratiois calculated by first calculating the equivalent weights of both the Acomponent and the B component by dividing their molecular weights by theaverage number of reactive sites per molecule. The actual componentweight of component A in grams divided by the equivalent weight ofcomponent A equals the equivalence of component A. The equivalence ofcomponent A times the equivalent weight of component B equals the actualweight of component B expressed in grams. The actual weights of bothcomponents A and B must be converted to volumetric units before they canbe set on the RIM machine. This is done by dividing the actual weightsof both components by their respective specific gravities. Very smallchanges can have catastrophic effects on properties. For example, a 2%change in a preselected 1:1.2 volumetric RIM ratio resulted in a 22%change in flexural modulus.

All currently available metering units measure the traveling speed ofthe piston and calculate the displaced volume flow rate of bothcomponents. It is necessary to record and control the volumetric flowrate ratio, to insure uniform polymer performance.

RIM injection pressures ranged between 2,000 and 3,500 psi. The typicalreaction time was 10 seconds, followed by an 8 hour post cure of 300° F.

The dinucleophilic B component and/or the A component may be a blend tocontrol the RIM reaction and the properties of the elastomer which isproduced. It was recognized early during our research that a blend ofdinucleophiles would be needed to realize all of the propertyrequirements for power transmission belts. The dinucleophiles wereselected on a temperature resistance and elastomeric tendency basis,i.e., a dinucleophile is selected which does not introduce thermallyunstable units, but does introduce flexible elastomeric units into thepolymer. Examples of dinucleophile blends (B side components) which haveproved to be useful in this invention are:

    ______________________________________                                        Jeffamine D-2000*     60%                                                     Jeffamine T-5000*     20%                                                     DuPont TAPED or TAPA**                                                                              10%                                                     Mitsui Bis-aniline M***                                                                              5%                                                     U.O.P. UNILINK 4200****                                                                              5%                                                     Jeffamine D-2000*     80%                                                     DuPont TAPED**        15%                                                     1,3-bis(3-aminophenoxyl) benzene                                                                     5%                                                     Jeffamine t-5000*     80%                                                     DuPont TAPA**         10%                                                     Mitsui Bis-aniline M***                                                                             10%                                                     ______________________________________                                         *A primary amine terminated aliphatic polyether available from Texaco.        **A primary amine terminated aliphatic chain available from DuPont.           ***A primary aromatic diamine available from Mitsui of Japan.                 ****A secondary aromatic diamine available from U.O.P. Corp.             

The Texaco Jeffamines are very long polyaliphaticether molecules whichmake up the bulk of the polymer, They are elastic, very flexible, andvery soft. The D series are diamines which promote linear chain growth,were as the T series is a triamine which promotes crosslinking betweenchains. The crosslinkages formed by the T series Jeffamine are, however,long branched chains of about 1,800 in molecular weight. Thiscrosslinkage does increase the resilience of the polymer but does notimprove the low tear resistance of the polymer.

To improve the tear resistance, molecules such as DuPont TAPA,tris(3-aminopropyl)amine, or TAPED, N,N,N',N', -tetrakis(3-aminopropyl)ethylenediamine are introduced, these polynucleophiles with short, lowmolecular weight aliphatic branches produce very tight crosslinkages ina honeycomb like polymer network. It is this polymer networking thatprovides the resilience, tear resistance, and wear resistance to thepolymer. The U.O.P. and Mitsui materials are hardness adjustors. Theyare short aromatic diamines with stiff para phenyl rings in theirbackbones.

It was also discovered that bismaleimides, bisitaconimidesbiscitraconimides, and bisvinylketones could also be blended to controlthe rate, or kinetics of the RIM reaction. It also provided a convenientmeans to introduce hard segments or tough segments into the polymer.Biscitraconimides react slower than bismaleimides and bisitaconimideswith dinucleophiles and impart a resilience to the polymer because ofits pendant methyl group. Bisvinylketones react much more rapidly withdinucleophiles than bismaleimides or bisitaconimides and provide a meansto increase the rate of reaction and reduce the post cure time andtemperature. Bisvinylketone linkages are not ring structures, thereforethey are more flexible than the bismaleimide, biscitraconimide, orbisitaconimide structures. The bisacetalketones on the other hand aretetra-functional and produce a very tight crosslinkage network. Theyharden and stiffen the polymer considerably. Examples of the most usefulbismaleimide, biscitraconimide, bisitaconimides, bisacetalketones,bistriazolinedione, and bisvinylketones used are: ##STR32##

A second approach to designing component A is to end cap a hightemperature resistance, secondary amine or mercaptan terminated, liquidprepolymer with a low molecular weight bisitaconimide. The theory beingthat the end capping groups, although high melting solids, are so smallcompared to the body of the molecule that they have little effect on themelting point of the total molecule. This proved to be true. Thebismaleimides or bisitaconimides represented by formula (X) or (XII-A)and more specifically by formula (XXV), (XXVI) or (XXVII) above areexamples of the end capping bisitaconimides or bismaleimides used.

A number of liquid A components of the general formula (XI) were madefrom mercaptan terminated polythioethers and polyoxythioethers fromProducts Research & Chemical Corporation by the following method.

PROCEDURE: A solution containing 1.0 mole equivalent of mercaptanterminated prepolymer, and 1 ml. of triethylamine in drydimethylformamide (DMF) was added drop wise to a mechanically stirredsolution of a bisitaconimide BII with the general formula (XII-A) ormore specifically formula (XXVI) or (XXVII) (2.1 mole equivalent) in dryDMF containing 10% of m-cresol, at 60° C. The mixture was stirred atthat temperature for 24 hours, then poured into a 10 to 1 solution ofmethanol and acetic acid with vigorous stirring. The mixture of solventswere decanted and the viscous polymer product was washed three timeswith methanol, then dried under reduced pressure. The bisitaconimide endcapped prepolymer then could be reacted with low moleculardinucleophiles such as Dupont DYTEK A (2-methylpentamethylenediamine)blended with TAPA (tris(3-aminopropyl)amine) and/or TAPED(N,N,N',N',-tetrakis(3-aminopropyl)ethylenediamine). Examples ofProducts Research & Chemical Corporation prepolymer blends are:

    ______________________________________                                               RW-2063-70                                                                             80%                                                                  RW-2064-70                                                                             20%                                                                  RW-2064-70                                                                             80%                                                                  RW-2065-70                                                                             20%                                                           ______________________________________                                         RW-2063-70 is a mercaptan terminated polyoxythioether prepolymer with an      average molecular weight of 6,500 and an average functionality of 2.75.       RW2064-70 has the same general structure as RW2063-70 differing only in       the molecular weight 2,850 and the functionality 2.0.                         RW2065-70 is a short chain dimercaptan with a molecular weight of 154.3,      functionality of 2.0, and the formula HSCH.sub.2 CH.sub.2 SCH.sub.2           CH.sub.2 SH.                                                             

Typical nucleophiles (B components) used to produce elastomers byreaction with A components prepared by endcapping liquid prepolymerswere piperazine, 2-methylpiperazine, methylene dianiline, DuPont DPTA(dipropylenetriamine), TAPA (tris(3-aminopropyl)amine), TAPED(N,N,N',N',-tetrakis(3-aminopropyl)-ethylenediamine),Cis-diaminocyclohexane and 1,12-dodecanediamine and1,13-tridecanediamine. This second method was used considerably duringthe early polymer evaluation studies because it was something we coulddo quickly to obtain polymer samples.

Another useful class of dinucleophiles is biscyclopentadienyl alkanesand, more particularly cyclopentadienyl alkanes having 1 to 15 carbonatoms in the alkylene bridge between the cyclopentadienyl rings. Thepreparation of these compounds is illustrated in ##STR33## Thesecompounds react with bismaleimide, bisitaconimide, biscitraconimide, andbistriazolinedione terminated prepolymers in a Diels Alder addition withthe formation of a polynorbornene elastomer. The basic reduction schemeis shown below. ##STR34##

The prepolymers of the present invention can also be reacted withbiscyclopentadienones to produce a RIM processable polyhydrophthalimide.This reaction is shown below. ##STR35##

The linking group L is usually divalent, however, trivalent andtetravalent linking groups such as ##STR36##

N,N,N',N',-tetrakis(3-etherpropyl)ethylenediamine are also possible.

This reaction is desirable because it proceeds with the loss of carbonmonoxide which makes the reaction irreversible.

Compounds of the formula (XXXVII) can be prepared as illustrated insynthesis Example 5.

For use in power transmission belts, the elastomers of the presentinvention must have the tensile, resiliency, solvent resistance andflexural characteristics which provide good service life as well as hightemperature resistance. Elastomers which are particularly preferred inthese applications have the following properties.

    ______________________________________                                        Tensile (kpsi)     1.5 to 3.5                                                 Elongation (%)     150 to 300                                                 Flexural Modulus (kpsi)                                                                          10.0 to 30.0                                               Shore hardness     75A to 45D                                                 Degradation temp. (in air)                                                                       > = 600° F.                                         ______________________________________                                    

RIM is the reaction of two highly reactive components insitu in a mold.In accordance with the present invention, the bismaleimide,bisitaconimide, biscitraconimide, bistriazolinedione, or bisvinylketoneand the dinucleophile are impingement mixed and injected into a mold ina conventional manner where they react to form the thermally stableelastomers of the present invention.

The invention is illustrated in more detail by way of the followingnon-limiting examples.

SYNTHESIS EXAMPLE 1 Endcapping of Dimercaptans

Dimercaptiodiethylsulifide (7.7 gr. or 0.1 mole equivalence) containinga few drops of triethylamine was added drop wise to a solution of (42.5gr. or 0.22 mole equivalence) of N,N',-bisitaconimidodiphenyl methane,in 500 ml. of freshly distilled m-cresol. The mixture was stirred atroom temperature for 2 hours, then warmed to 60° C. A solution of (303.7gr. or 0.213 mole equivalence) of RW-2064-70, a mercaptan terminatedpolythioether prepolymer available from Products Research & ChemicalCorp., in 500 ml. m-cresol was added slowly to the mixture and theresulting mixture was mechanically stirred for 20 to 24 hours at 60° to70° C., then for an additional 2 hours 100° C. The mixture was cooled to80° C. and (40.5 gr. or 0.21 mole equivalence) of bisitaconimidodiphenylwas added, then stirred overnight. The resulting mixture was poured intoa solution of methanol containing 10% acetic acid in a stainless steelWaring blender and the viscous polymeric material was broken to form aresinous liquid polymer, separated in a separatory funnel from themethanol, the prepolymer was washed three times with methanol, and driedin a rotoevaporator under vacuum at 60° C. for 3 hours.

SYNTHESIS EXAMPLE 2 Endcapping of Dimercaptans

A solution of 0.1 mole equivalent of mercaptan terminated liquid polymerRW-2066-70, available from Products Research & Chemical Corp., in 1liter dry DMF was added dropwise to a mechanically stirred solution of4,4-bisitaconimidocumyl metabenzene, available from MitsuiPetrochemicals Corp., (2.0 mole equiv.) in dry DMF, containing 10% ofm-cresol and 1 ml. of triethylamine, at 60° C. The mixture was stirredat that temperature for 24 hours, then poured into a 10 to 1 solution ofmethanol and acetic acid with vigorous stirring. The solvents weredecanted from the viscous prepolymer product and washed three times withmethanol, then dried in a rotoevaporator under vacuum at 60° C. for 4hours. ##STR37## The resulting bisitaconimide end capped prepolymer wasreacted with various diamines such as DuPont C₁₂ DIAMINE, 1,12-dodecanediamine, or DuPont TAPA, tris(3-aminopropyl)amine, or2-methyl piperazine to yield amorphous dark brown to light amberthermoset plastic resins.

SYNTHESIS EXAMPLE 3 Preparation of Polyether Diamines

In a 500 ml. round bottom three neck flask outfitted with a refluxingcondenser, mechanical stirrer, and addition separatory funnel was added150 ml. DMAC, 15.19 gr. of potassium carbonate, and 32.18 gr. of metachloroaniline. This mixture was stirred and heated to 150° C. After themixture had a chance to stabilize at 150° C. for 30 minutes 12.43 gr. ofhexanediol was added drop wise to the flask over a 1 hour period. Theflask was allowed to reflux overnight or 18 hours. The flask was thenallowed to cool down to room temperature. The contents were filtered andthe solid potassium carbonate was discarded. The filtrate was then mixedwith water and 100 ml. of chloroform. The chloroform diamine layer waswashed with water 4 times. The organic layer was then distilled undervacuum. The chloroform and water fractions were discarded, the lastfraction was saved. The reaction yield was 83.0% of 6,6'-diaminom-phenoxyhexane. This nucleophilic aromatic substitution reaction wasused to make a variety of aromatic amines and aromatic amine terminatedaliphatic ether diamines. ##STR38##

SYNTHESIS EXAMPLE 4 Preparation of Liquid Bisamleimides

To a vigorously stirred solution of 6,6'-diamino m-phenoxyhexane (0.1mole) in acetone under a nitrogen atmosphere, maleic anhydride (.22mole) was added, the temperature outside being maintained at a constant20° C. The pale yellow solid of bis-maleamic acid soon obtained onaddition of maleic anhydride, was vigorously stirred for a further 0.5hour to complete the reaction. To the continuously stirred suspension ofcompound in acetone were added acetic anhydride (70 ml., excess) andfused sodium acetate (5 to 6 gr.), and the acetone was allowed toreflux. Refluxing and stirring were continued until the solution becameclear (2 to 2.5 hours).

The clear brownish yellow solution was poured into ice water and 100 ml.of chloroform was added and the whole thing was shaken in a separatoryfunnel. The organic layer was washed with water containing sodiumbicarbonate 4 times by shaking it in a separatory funnel. The organiclayer was then passed through a filtration chromatography columncontaining silica gel. The chloroform was then removed by distillationunder vacuum in a rotoevaporator. The resulting 6,6'-bismaleimidom-phenoxyhexane is a yellowish orange viscous liquid at roomtemperature. ##STR39##

SYNTHESIS EXAMPLE 5 Preparation of the Biscyclopentadiene

A mixture of meta-dibromobenzene (1 mole), triphenyl phosphine (20 gr.),copper iodide (3 qr.), and palladium (II) acetate (1 gr.), in 1 liter ofdry triethylamine is heated and stirred at 100° C. Phenylacetylene (2.5moles), is added slowly and the resulting mixture is refluxed for 8hours. The mixture is cooled and the solid product washed with ether,then with water, and methanol. The product I, is then air-dried and usedin the next step. ##STR40##

Step 2

A mixture of potassium permanganate (3 mole),1,4-bis(phenylethynyl)arene, product I (1 mole), water (6 liters),methylene chloride (5 liters), acetic acid (400 ml.), and phase transferagent (Adogen 464 methyltrialkyl (C₈ -C₁₀)-ammonium chloride availablefrom Aldrich Chemical Co.) is mechanically stirred and refluxed for 6hours. After cooling, sodium-hydrogen sulfite (20 gr.) is added slowlyto reduce any unreacted permangante. After 15 minutes the solution isacidified with 1 liter of concentrated hydrochloric acid and theprecipitated manganese dioxide is reduced by addition of excessconcentrated sodium hydrogen sulfite solution. The aqueous phase isseparated and extracted with dichloromethane (3 liters). The combinedorganic layer is washed with 5% sodium hydroxide solution, driedmagnesium sulfate, filtered, and concentrated to give the product II.##STR41##

Step 3

A one mole equivalent sample of product II and two mole equivalent ofdibenzylketone is heated for 4 hours in a mechanically stirreddichlorobenzene solution. The mixture is diluted with addition of hexaneand the solid product is filtered, washed with hexane and dried.Purification of this product may be carried out by recrystallizationfrom acetone or methyl ethyl ketone. ##STR42##

SYNTHESIS EXAMPLE 6 Preparation of Biscyclopentadienyl Alkane

To a solution of sodium cyclopentadienyl (2 mole equivalence), in drytetrahydrofuran (THF) under nitrogen atmosphere and ice bathtemperature, is added drop wise a solution of 1,6-dibromohexane,selected from those with the general form shown below, (1 moleequivalence), in dry THF. When the addition is complete, the mixture isstirred at 5° to 10° C. for 6 to 12 hours. The resulting solution ispoured into an ice-cold dilute hydrochloric acid (5%) and the product isisolated by filtration or extraction. ##STR43##

SYNTHESIS EXAMPLE 7 Preparation of Activated Bisvinylketone

To a solution of suberoyl chloride. CICO(CH₂ )₆ COCI, (1 moleequivalence) and aluminum chloride (2.2 mole equivalence) in methylenechloride at 0° C., is added drop wise a solution of trimethylvinylsilane (2.4 mole equivalence) in methylene chloride. The mixture isstirred at 0° to 5° C. for 6 to 10 hours, then poured in ice-cold 10%hydrochloric acid. The mixture is shaken in a separatory funnel,methylene chloride layer is washed with water, dried (MgSO₄). Thesolution is then filtered and the methylene chloride is distilled undervacuum in a rotoevaporator at 50° C. to give bisvinylketone product.##STR44##

SYNTHESIS EXAMPLE 8 Preparation of Liquid Bisitaconimides SpecificallyBII P250)

The Polamine 250 contains a lot of water. It must be dried before using.This is accomplished by placing the open can in a vacuum oven overnight, set at 100° C. and 1 mm of H_(g). Care must be taken to apply thevacuum only after the material has arrived at temperature and then veryslowly to prevent the material from foaming over.

The acetone is also dried before using. This is accomplished by stirring1 lb. of Drierite, (W.A. Hammond Drierite Co.), in 10 liters of acetonesealed in a 12 liter flask over night The acetone is then redistilledand stored in wax sealed septum bottles.

All glassware is dried in a hot air oven set at 120° C. over night. Theglassware is assembled hot, sealed, and purged with dry Argon gas beforeit has a chance to cool down.

Given

Polamine 250, molecular weight=474, functionality=2.

Itaconic Anhydride, molecular=112

Acetic Anhydride, molecular weight=102.09

Sodium Acetate, molecular weight=82.03

Computations

250 grams of Polamine 250/474=0.5274 moles of Polamine

112·0.5274·2=118.14 grams of Itaconic anhydride

118.14·1.1=129.95 grams, 10% extra Itaconic anhydride

Preparation of the Diamic acid

The polamine 250 is Preheated to 70° C. and weighed directly into thebottom of a hot, Predried, 5 liter, 3 neck (24/40 joints), fluted side,reactor flask. The flask is quickly assembled, sealed, and purged downwith dry Argon gas. After the flask and diamine has cooled down to 40°C., 2,250 ml. of dried acetone is added and the flask is slowly stirreduntil all of the Polamine 250 has dissolved.

Weigh the maleic anhydride in a Predried, glass stoppered, 500 ml.Erlenmeyer flask. Add a magnetic stirring bar and 400 ml. of predriedacetone. Stir the mixture until the itaconic anhydride has dissolved.Pour the solution into a predried 500 ml dropping, pressure equalizing,funnel mounted on the reactor setup. Rinse out the Erlenmeyer flask withan additional 50 ml. of dried acetone and add it to the dropping funnel.

Chill the reactor down to 12° C. and start the addition of the Itaconicanhydride-acetone solution drop wise to the reactor. During the additionstep the reactor is stirred vigorously but not to the point ofsplattering. Nearly immediately the reactor solution will turn yellow,and after 10 to 20 minutes, depending on the rate of addition, a creamyyellowish precipitate will start to form.

Care must be taken during this step, if too little acetone is used thereactor can setup hard and break.

After the addition is complete, about 3 to 4 hours, the ice water bathis removed and the reactor is allowed to warm up naturally to roomtemperature, about 23° C. The addition funnel is rinsed with 50 ml. ofdried acetone and this $ allowed to slowly drip into the reactor. Thereaction is allowed to continue over night, about 12 hours. Morning thenext day the reactor will contain a creamy off white colored slurry,very thick.

Longer reaction time will not hurt the product.

Ring Closing Conditions

The conditions for closing the amic acid structure to form theItaconimide ring is very important to both temperature and theproportions of sodium acetate and acetic anhydride used. For bestresults use 0.2 moles of sodium acetate, and 2 moles of acetic anhydrideper mole of the amic acid group. The reactor temperature should not beallowed to rise above 27° C. at any time. For best results reactortemperatures should be controlled between 23° and 27° C. The reactiontime is also a concern, typically overnight or 12 hours is sufficient tocomplete the reaction. It can be allowed to continue longer if desired,but should be a bright yellow, if there is even the slightest hint ofamber or brown to the mixture the reactor has overheated or the reactionhas gone too long. The product contains impurities and may not bestable.

Computations

2·0.2·0.5274·82.03=17.305 grams of sodium acetate

2·2·0.5274·102.37=215.37 grams of acetic anhydride

Preparation of the BII

Both the sodium acetate and the acetic acid are added directly to thereactor.

Care is taken to get all of the materials into the reactor and not toleave any clinging to the sides.

The addition funnel is removed and the reactor is stoppered with a glassthermometer adapter stopper and a 10° to 100° C. thermometer. Within 20minutes the creamy (off white colored) precipitate will start todissolve and the reactor contents will take on a bright yellow color.The reactor should be stirred vigorously to break up lumps and tofacilitate in dissolving the precipitate. After 12 hours the contents ofthe reactor will be a very intense bright yellow, almost clear, withsodium acetate crystals and some crystallized BII in the Bottom.

Workup of the BII

The contents of the reactor are first vacuum filter through a coarseglass fretted Buchner funnel. The sodium acetate left in the funnel iswashed with fresh acetone to dissolve any BII that is trapped in thesalt. The filtrate is again vacuum filtered through a fine glass frettedBuchner funnel. The salt remaining in the funnel is again washed withfresh acetone The filtrate is then slowly added to five liters of acold, 10° to 20° C., solution of sodium carbonate in distilled water,105.99·4·0.5274=223.6 grams of sodium carbonate per 5 liters of water.Care must be taken that the solution does not foam over.

After all of the filtrate has been added and the effervescing hasceased, the stirring is stopped and the solution is allowed to settle.The aqueous layer is decanted and discarded. The crude BII isredissolved in to 1 liter of fresh acetone and the wash cycle isrepeated once again with a dilute solution of sodium carbonate indistilled water.

The BII is again redissolved in 1 liter of acetone and washed in justdistilled water. This step may be repeated two or more times until thereis not even a hint of acetic acid left.

The BII is then redissolved in 500 ml. of acetone and transfered to arotary evaporator flask. The flask is then placed on a rotary evaporatorand heated to 80° C. and the flask is evacuated to a pressure of 1 mm ofHg. This process is carried out for 10 to 12 hours. The flask is thenattached to a Kugelrohr still, the temperature is maintained at 80° C.but the pressure is lowered to 0.02 mm Hg. The BII is distilled for anadditional 10 to 12 hours. The flask is then purged with N₂ stopperedwith a glass stopper and labeled.

The resulting BII will be a light golden yellow to a light amber yellowcolored, syrupy liquid Which may in time partially crystallize. Theapproximate values for SP. Gr.=1.172 grams/cubic centimeter, molecularweight=638, and functionality=2. It also becomes very fluid at 65° C.

Having described the invention in detail and by reference to specificembodiments thereof, it will be apparent that numerous modifications arepossible without departing from the spirit of the invention as definedin the following claims.

What is claimed is:
 1. A prepolymer of the formula: ##STR45## where LGis a linking group.
 2. The prepolymer of claim 1 wherein LG isrepresented by the formula: ##STR46## where L represents a flexiblelinking group.
 3. The prepolymer of claim 2 wherein L is selected fromthe group consisting of ##STR47## an alkylene bridge of 1 to 5 carbonatoms, ##STR48## where E is --O--, ##STR49## u is 1 to 7; t is 1 to 5; mis 1 to 12; p is 3 or 5; and Ar represents an arylene group.
 4. Theprepolymer of claim 3 wherein said prepolymer is selected from the groupconsisting of ##STR50## where q is 1 through 7; ##STR51## where E is--O--, ##STR52## o is 4, 5, 6, 8, 9, 12, or 13 and p is 1, 3, or 5;##STR53## where E, o, and p are defined as in formula (XXVII), ##STR54##where r is 3 or 5, and ##STR55##
 5. In a process for reaction injectionmolding, the improvement which comprises reacting a dinucleophile theformula (XV) or (XVI) ##STR56## where R is a hydrogen atom or a loweralkyl group and W' is a polyether, aromatic or aliphatic, aliphaticpolythioether, aliphatic polyetherthioether or a co-polymer of aromaticand aliphatic polyethers or polythioethers with a prepolymer of theformula ##STR57## where LG is a linking group.
 6. The process of claim 5wherein LG is represented by the formula: ##STR58## where L represents aflexible linking group.
 7. The process of claim 6 wherein L is selectedfrom the group consisting of ##STR59## an alkylene bridge of 1 to 5carbon atoms, ##STR60## where E is --O--, ##STR61## u is 1 to 7, t is 1to 5, m is 1 to 12, p is 3 or 5; and Ar represents an arylene group. 8.The process of claim 7 wherein said prepolymer is selected from thegroup consisting of ##STR62## where q is 1 through 7, ##STR63## where Eis --O--, ##STR64## o is 4, 5, 6, 8, 9, 12, or 13 p is 1, 3, or 5,##STR65## where E, o and p are defined as in formula XXVII, ##STR66##where r is 3 or 5, ##STR67##
 9. The process of claim 5 wherein W' isrepresented by the formulas (XVII)-(XIX)

    --R.sup.1 --(--O--R.sup.2 --S--R.sup.3 --).sub.x --        (XVII)

    --(--R.sup.1 --O--R.sup.2 --).sub.x --                     (XVIII)

    --(--R.sup.1 --S--R.sup.2 --).sub.x --                     (XIX)

where R¹, R² and R³ represent straight or branched chain alkylene orarylene groups having 2 to 12 carbon atoms and x is 2 to
 70. 10. Apolymer obtained by reacting a prepolymer as defined by the formula##STR68## where LG is a linking group, and copolymers thereof with adinucleophile
 11. The polymer of claim 10 wherein said polymer is acopolymer of said prepolymer with a dinucleophile.